Four ghosts.

Anyone who played Pac-Man as a child remembers the first minute as chaos. Four ghosts leave the pen in the middle of the maze and close in from every side, and the player turns and turns again until one of them catches him. Then, somewhere around the hundredth quarter, a different game appears. The red ghost is always behind you. The pink one is always trying to get in front. The orange one comes close and then, for no visible reason, loses interest. The panic turns into reading, and the reading turns into something like calm.

That shift is the real achievement of Pac-Man, and it was designed. The ghosts look like a pack, but each follows a rule of its own, and the rules are simple enough that a determined child can learn them by watching. The game is usually remembered for its cheerful hero. It is better understood as one of the first to offer a player the satisfaction of figuring out an intelligence and finding that it had been fair all along.

Toru Iwatani led a nine-person team at Namco in Tokyo, and development began in early 1979. Arcades at the time were full of shooting games played mostly by young men, and Iwatani wanted something that would bring women and couples inside. He settled on eating as the theme. The shape of the hero came partly from a pizza with a slice missing and partly from a rounded-off version of the Japanese character for mouth, kuchi.

The game went on sale in Japan on May 22, 1980, as Puck Man. Namco’s executives worried that vandals in America would turn the P on the cabinet into an F, so for export the name became Pac-Man. Midway Manufacturing, which already had a hit with Taito’s Space Invaders, licensed it and released it in North America in October 1980. By 1982 about 400,000 cabinets had been installed around the world.

When they are chasing, the ghosts are not choosing among options. Each one picks a single tile on the board as its target and heads for it. Blinky, the red ghost, targets the tile Pac-Man is standing on, so he is always at your back. Pinky, the pink ghost, targets a spot four tiles ahead of the direction Pac-Man is moving, so she tries to cut him off. Inky, the light blue ghost, takes a point two tiles ahead of Pac-Man and doubles the distance from Blinky to that point, which means his path depends on where Blinky happens to be. Clyde, the orange ghost, chases directly when he is eight tiles or more away and retreats toward his home corner when he gets closer. Several times in each level, all four break off the chase and scatter, each heading for its own corner of the maze.

In Japan their names describe their jobs. Blinky is Oikake, the chaser, and Pinky is Machibuse, the ambusher. Inky is Kimagure, the fickle one, and Clyde is Otoboke, which roughly means the one who plays dumb. The names are a designer’s shorthand, and they are accurate. Four lines of logic produced four personalities, and the personalities were legible to anyone who paid attention.

That legibility is what made the game generous. A player who learned the rules could stop fleeing the crowd and start handling each ghost as what it was: never turn straight into Pinky’s path, keep an eye on Blinky when Inky draws near, and let Clyde wander, because he will turn away on his own. Energizers, saved until two or three ghosts were close, became a matter of timing rather than luck. None of this was hidden. It was simply waiting to be noticed.

The follow-up began as another company’s product. General Computer Corporation, a small American firm, had built an enhancement kit for Pac-Man machines called Crazy Otto. After a legal fight with Atari left it unable to sell such kits on its own, it took the game to Midway, which bought it and worked with the company and Namco to finish it. As the GCC co-founder Doug Macrae has recalled, Namco’s president, Masaya Nakamura, looked at the new heroine and replied, “Love the concept, get rid of the hair.”

Ms. Pac-Man reached arcades in February 1982 with four mazes instead of one, fruit that bounced around the board and ghosts that were harder to predict. It sold about 125,000 cabinets by 1987, and Namco collected royalties on every one. The change in the ghosts is telling. Players had solved the first game so thoroughly that the sequel had to make its enemies a little less knowable, and the whole later history of game design can be read as a negotiation over exactly how much of the machine a player should be allowed to understand.

Pac-Man has an ending, and nobody designed it. The level counter is stored in a single byte, and when the game tries to draw the fruit for level 256, the number overflows. The right half of the maze fills with garbled letters and numbers, and the level cannot be finished. The highest possible score, 3,333,360 points, requires eating every dot, energizer, fruit and blue ghost on the first 255 levels without losing a life, then using all six lives to collect what little the broken screen allows. The game Iwatani built to be read ends where the machine underneath it could no longer read itself.

It is tempting to be sentimental about this, and a little sentiment is earned. The systems that chase most of us now, deciding what we see next and what we are shown to buy, do not publish their rules, and nobody expects to learn them by watching. Pac-Man made a different offer. It put four pursuers in a box, gave each of them one thing to want and let anyone with quarters and patience work out what that thing was. The maze was frightening for a minute. After that, it was a place where paying attention was enough.